YA: Simply Adding and Removing Points From Users WOC

<?php
session_start();

/*    Place your Database Connection Stuff Here, or Include the connection file    */

/*    Functions    */
function getPts($username){
    $result = mysql_query("SELECT pts FROM users WHERE user_name='{$username}' LIMIT 1") or die('MySQL Query Error: ' . mysql_error());
    return mysql_fetch_object( $result )->pts;
}
function updatePts($username, $pts){
    $result = mysql_query("UPDATE users SET pts=pts+({$pts}) WHERE user_name='{$username}' LIMIT 1") or die('MySQL Query Error: ' . mysql_error());
    return $result;
}
if( $_SERVER['REQUEST_METHOD'] === 'GET' ){
    $username = mysql_real_escape_string( $_SESSION['username'] );
    $pointsAvail = $_SESSION['pts'] = getPts($username);
    if($pointsAvail > 0){
        echo '
            <form method="post">
                ' . $username . ', you currently have: <span style="font-weight: bold;">' . $pointsAvail . '</span> pts Available to transfer.<br>
                Send: <input type="text" name="formValue" value="' . $pointsAvail . '"> pts<br>
                To: <input type="text" name="recipient"><br>
                <input type="submit" value="Send Pts">
            </form>
        ';
    }else{
        echo 'Sorry, ' . $username . ', you do not have any points to transfer.';
    }
}else{

    /*    Form Has Been Submitted, Update Necessary Fields    */
    $username = mysql_real_escape_string( $_SESSION['username'] );
    $recipient = mysql_real_escape_string( $_POST['recipient'] );
    $formValue = abs( $_POST['formValue'] );
    $errorMsg = '';

    /*    Error Checking    */
    if(strlen($recipient) === 0){
        $errorMsg .= 'You need to enter a recipient.<br>';
    }
    if($formValue > $_SESSION['pts']){
        $errorMsg .= 'You do not have enough points (' . $_SESSION['pts'] . ' pts) to transfer ' . $formValue . ' pts.<br>';
    }
    if($recipient === $username){
        $errorMsg .= 'There\'s no point in sending points to yourself.<br>';
    }else if(!@mysql_query("SELECT pts FROM users WHERE user_name='{$recipient}' LIMIT 1")){
        $errorMsg .= 'The Recipient selected does not appear to exist.<br>';
    }

    /*    If Errors, display Message and end    */
    if( strlen($errorMsg) > 0){
        echo 'The following errors occurred: <br>' . $errorMsg;
    }else if( updatePts( $recipient, $formValue ) && updatePts($username, ($formValue * (-1))) ) {
        $_SESSION['pts'] -= $formValue;
        echo '<h3>Success</h3><p>You gave sent ' . $formValue .' pts to ' . $recipient . '.</p>' .
                '<p>You currently have: ' . $_SESSION['pts'] . ' pts remaining.</p>';
    }else{
        echo '<h3>Error</h3><p>An internal server error has stopped this process. Please try again in a few minutes.</p>';
    }
}